1. Field of the Invention
The present invention relates to an improved method and apparatus for separating non-fibrous particulates from fibers. More particularly, the present invention provides an improved method and apparatus for separating entrained and/or adherent elastomeric particulates, such as crumb rubber, from fibers such as nylon or polyester.
2. Description of the Prior Art
The disposal of discarded rubber vehicle tires, especially for cities, states and industries throughout the United States, has been a problem ever since transportation first began to use tires. Billions of discarded tires occupy landfills and stockpiles, which as they have grown, governmental and corporate bodies have worked to reduce. Some states charge disposal fees and/or sales surcharges of $1.00 to $2.00 per tire.
Indiscriminate discarding of rubber vehicle tires poses environmental and health problems. Waste tires provide breeding grounds for insects and rodents, and are not biodegradable. Further, their geometry being that of a noncompactable hollow toroid shape is voluminous and brings about the premature filling of dump sites.
The difficulty of discarding worn out rubber tires has led to investment in disposal technologies related to either volumetric reduction or material recycling. Recycling of rubber tires is difficult because of problems associated with their multi-component non-homogenous construction. A tire typically comprises rubber tread and sidewalls reinforced with enmeshed layers of steel wire and reinforcing fabric. Further, the rubber is usually vulcanized resulting in a toughness for the tire that contributes to its associated indestructibility.
The majority of the techniques used to recover recyclable components from waste tires requires initial physical processing, such as shredding or cryogenic pulverization, followed by further refining by some secondary process, such as converting the materials into a reusable form by chemical digestion, mechanical reclamation, destructive distillation, etc. In cryogenic crushing or pulverizing, liquid nitrogen is used to lower the temperature of the tire to about -300 degrees Fahrenheit. At such low temperatures, rubber hardens and is easily fractured into tiny granules or particulates, leaving steel wire and reinforcing fibers relatively unaffected. The steel wire is removed by electromagnetics and the reinforcing fibers are removed by sieving. The cost of cryogenic processing is relatively high, and typically suffers from inadequate recovery of rubber. The remaining rubber granules and fibers are usually disposed of in landfills.
In a related co-pending patent application Ser. No. 09/107,760, filed on Jun. 30, 1998 and entitled "A Method for Separating Elastomeric Particulates from Fiber", a method is disclosed for separating non-fibrous particulates from fibers by contacting a pulverized mixture with a plurality of revolving mixture-engaging structures to cause the revolving mixture-engaging structures to engage the fibers and separate the fibers from the non-fibrous particulates. The produced non-fibrous particulates typically contain residual fibers which are removed in a reclaiming zone containing a saw cylinder, a doffing brush cylinder, and a cylinder with protruding rods. The method disclosed in patent application Ser. No. 09/107,760 has limited capabilities of recovering both non-fibrous particulates and fibers.
Therefore, what is needed and what has been invented is an improved method for separating and recovering a higher percentage of both non-fibrous particulates and fibers from a pulverized mixture without the deficiencies associated with the prior art in recovering recyclable components from waste tires. What is further needed and what has been invented is an improved, inexpensive and effective method for recovering rubber particulates from a pulverized tire mixture. What is also further needed and what has been invented is an improved method for separating particulate rubber (e.g., crumb rubber) from fibers (e.g., polyester or nylon fibers).